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Adaptive variation in the mammalian respiratory system in relation to nergic demand: VI. The pulmonary gas exchanger

Respiration Physiology, ISSN: 0034-5687, Vol: 69, Issue: 1, Page: 81-100
1987
  • 47
    Citations
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  • 15
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Metrics Details

  • Citations
    47
    • Citation Indexes
      47
  • Captures
    15

Article Description

This paper explores the question whether the morphometric diffusing capacity of athletic dogs and ponies isl arger than that of goats and calves, in proportion to the 2.5-fold higher limit for O 2 consumption in the athletic species. Comparing pony and calf we find the lung volumes, the gas exchange surfaces, and the capillary volume to be about 1.5-fold larger in the pony, whereas red cell size and the barrier thicknesses are about the same. Lung and capillary volumes, as well as the gas exchange surfaces do not differ significantly between dog and goat, whereas red cell size, capillary hematocrit and plasma barrier thicknesses differ greatly. The membrane diffusing capacity calculated from morphometric data is about 1.25 times higher in the athletic species. The O 2 conductance of the blood is higher in the athletic species because of their higher hemoglobin content, its value also depends on the assumptions made with respect to the reaction kinetics of the blood (Θ O2 ). The results are only consistent if the initial reaction rate of O 2 with erythrocytes is assumed to be independent of red cell size. In this case we find that D L O2 of the athletic species is 1.5 times larger than that of the less aerobic species, and that the pressure head for O 2 diffusion is also 1.5 times larger. The 2.5-fold greater O 2 transfer capacity of the lung of athletic animals is therefore achieved by increasing by equal parts the structurally determined diffusing capacity and the driving force for O 2 diffusion.

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